I. embryonic development of the CNS A. neurulation is the formation of the CNS in the embryo invagination of dorsal ectoderm (outer layer of embryo) this process is induced (caused) by the notochord BIOL 2304 Fall 2008Chapter 131

BIOL 2304 Fall 2008Chapter 132

BIOL 2304 Fall 2008Chapter 133

1. neural tube transverse sections BIOL 2304 Fall 2008Chapter 134

dorsal view the cranial end becomes the brain the rest becomes the spinal cord BIOL 2304 Fall 2008Chapter 135

2. neural crest cells (green cells on slide 3) invaginate after neural tube cells and are not incorporated into the tube they form the sensory nerve cells BIOL 2304 Fall 2008Chapter 136

3. cells in the wall of the neural tube proliferate and migrate to surround the tube they form gray matter 4. these cells’ axons grow outwards away from the tube they form white matter BIOL 2304 Fall 2008Chapter 137

BIOL 2304 Fall 2008Chapter 138

B. expansion of the cranial end of the neural tube produces vesicles the walls of vesicles expand and thicken to form solid parts of brain fluid-filled cavities remain inside the vesicles (ventricles) BIOL 2304 Fall 2008Chapter 139

brain vesicles BIOL 2304 Fall 2008Chapter 1310

C. the brain bends to fit into the cranium midbrain flexure cervical flexure Why doesn’t the cranium just get larger? BIOL 2304 Fall 2008Chapter 1311

D. during expansion, the cerebrum grows outwards and around the diencephalon BIOL 2304 Fall 2008Chapter 1312